This invention relates to a communication system, and more particularly, to a communication system in which SIP session control is used.
The third generation mobile network system aims to provide various multimedia services of high quality and high speed. The multimedia services include voice, data, video and the like. The 3rd Generation Partnership Project (3GPP) has been promoting standardization of an “All IP based mobile communication network” to provide a multimedia service using an internet protocol (IP) technique on a packet switching network.
A session control system in the All IP based mobile communication network is called an IP multimedia subsystem (IMS). The IMS has been used in the session control technique in the next generation network (NGN).
A session initiation protocol (SIP) is used as a session control protocol (For example, see IETF RFC3261, “SIP: Session Initiation Protocol §4”). The SIP is a protocol for performing session control of the IP multimedia communication specified for internet engineering task force (IETF).
A voice over IP (VoIP) is a representative service using the SIP. The VoIP is a technique which transmits/receives voice information on the IP network. The VoIP communication using the SIP requires a setting of a virtual speech path (a session) between communication devices which transmit/receive voice information. Voice data which is IP packetized is transferred through the set virtual speech path. In the VoIP communication, the SIP controls initiation, maintaining and termination of sessions between the communication devices.
Media information such as attributes of the voice data is determined at the session initiation. The media information is notified using a session description protocol (SDP) included in a SIP message. The SDP describes various pieces of session information (an IP address, a port number, a media type, for example).
Further, an application programming interface (API) is being considered for being able to use a communication service provided by a provider from a Web service provided by a third party.
The Parlay Group is a group that specifies an open API which does not depend on a network or a vendor. The Parlay Group is planning to use “Parlay-X” as the open API. “Parlay-X” specifies APIs for the purposes of the usage in a Web service environment, and the Web service of which usage is not limited to an implemented language. The “Parlay-X” provides Web developers with abstracted communication APIs.
The APIs specified in the “Parlay-X” include, for example, 3rd party call control (3PCC) which provides a two-party speech service by initiating from a Web application side. (For example, see 5th Draft ES 202 504-2 Parlay X 3.0, “Part 2: Third Party Call”, [online], August 2007).
The Parlay Group cooperates with the European telecommunications standard institute (ETSI) and the 3rd generation partnership project (3GPP). The “Parlay-X” is published by the three groups and defines a standard open interface; however, how the “Parlay-X” is implemented is not specified.